Shifter interlock for an automatic transmission

ABSTRACT

An automotive shifter interlock in which a slidable shift lever release member is mechanically locked in a shift-release-inhibit position by the combination of an electromagnet bolt and an ignition switch bolt. The ignition switch bolt mechanically locks the electromagnet bolt in a position locking the shift lever release member even though no power is supplied to the electromagnet. After the ignition switch is closed and the ignition switch bolt withdrawn, the electromagnet continues to provide an electromagnetic lock until the brake pedal is depressed.

This application is a Continuation of U.S. Pat. application Ser. No.08/410,909, filed Mar. 27, 1995, now U.S. Pat. No. 5,647,818.

FIELD OF THE INVENTION

This invention relates to shifter interlocks for automotive vehiclesequipped with automatic transmissions and more particularly to a shifterinterlock involving the combination of both electromagnetic and purelymechanical controls.

BACKGROUND OF THE INVENTION

Operator manipulation of the automatic transmission of a motor vehicleis typically accomplished by way of a shift lever mounted either on ornear the steering column of the vehicle or in or adjacent a consolemounted on the floor of the vehicle between the driver's seat and thefront passenger seat. The shift lever is mounted for primary movementbetween a PARK position and the Forward and Reverse driving positions,usually separated by a "Neutral" position. The shift lever is alsomounted to provide a release movement, usually at right angles to theprimary movement, through which a pawl is lifted out of and seated intoa detent to hold the shift lever in the PARK position and preventinadvertent movement of the lever in the primary mode; i.e., from PARKto one of the drive positions. The release movement can be implementedin several ways including (a) lateral shift lever movement, (b)fore-and-aft shift lever movement, (c) axial shift lever movement, and(d) depression of a push button.

Beginning in about the late 1980's automobiles manufactured for saleand/or use in the United States have been equipped with one of severaltypes of shift lever interlocks, the most typical being asolenoid-implemented interlock which prevents the shift lever from beingmoved out of the PARK position until the operator has activated theignition circuit and depressed the brake pedal. Depression of the brakepedal closes a switch normally associated with the brake light circuitto either supply or cut off the supply of power to a solenoid coilthereby to position an armature connected pin. Depending on theparticular implementation of the interlock the solenoid pin can be usedto latch either the shift lever primary movement or the releasemovement.

The interlock, although commonly involving the brake light circuit, canbe associated with any automotive system capable of producing anappropriate electrical signal; e.g., a seat belt switch or a seatoccupancy switch. Examples of such interlocks are illustrated in U.S.Pat Nos. 4,854,193 and 4,986,399.

U.S. Pat No. 4,887,702, assigned to United Technologies Automotive,Inc., discloses an interlock for a floor mounted shifter in which both amechanical ignition lock and a brake/shift lock solenoid are connectedto a pivotally movable PARK/LOCK member in the shifter by means of oneor more cables. According to the further disclosure of U.S. Pat. No.5,027,929, also assigned to United Technologies Automotive, the cableimplemented interlock of U.S. Pat No. 4,887,702 requires not only one ortwo relatively expensive cables but also requires a relatively precisecable length adjustment procedure during installation to ensure that thesolenoid will operate properly.

SUMMARY OF THE INVENTION

The present invention provides a shifter interlock using anelectromagnet to inhibit shifter operation until a specified condition,such as brake pedal depression, is satisfied.

In general the invention comprises an automotive shifter having a shiftlever and an axially movable shift lever release member which is movablebetween a first position in which primary shift lever movement isprevented and a second position in which primary shift lever movement ispermitted. The axial or linear movability of the shift lever releasemember is determined by an electromagnet which locks or releases theshift release member according to the status of the specified condition.In a preferred embodiment of the invention, the movable armature of theelectromagnet is also mechanically tied to the vehicle ignition suchthat the armature may not be moved to a shifter operable position untilthe ignition lock is released. The ignition key lock includes a bolt orpin extendable into contact with the electromagnet armature toalternatively block and release movement of the bolt in accordance withthe condition or status of the ignition key lock.

As a result the purely mechanical ignition key/shifter interlock issuperimposed on the electromagnetic interlock so as to provide amultiple condition interlock which can be implemented without cables andwithout the complex installation procedures associated with cables.

In the illustrated embodiment the shift lever is steering column mountedand both the ignition key lock and the electromagnet are convenientlymounted on the steering column in close physical proximity so as to bein direct association with the shifter release member. In the preferredform the electromagnet holds a locking bolt in engagement with a notchin the shift lever release member and the ignition key lock operates inthe manner of a bolt type lock to alternatively enable and inhibitmovement of the bolt away from engagement with the release member.

The invention uses an electromagnet holding device as opposed to themore conventional solenoid. In the latter device, energization of anelectrically conductive coil creates an electromagnetic field whichinduces axial movement of a ferromagnetic core positioned inside thecoil. An electromagnet holding device, by contrast, comprises aferromagnetic canister which is magnetized when an electricallyconductive coil disposed therein is energized. A non-ferrous bolt orshaft is slidingly mounted in a hole passing through the central axis ofthe canister and a ferromagnetic armature disk is attached to one end ofthe bolt. If the armature disk is in contact with the open end of thecanister when it becomes magnetized by the energization of the coil, thedisk will be held firmly in contact with the canister. If the disk isnot in contact with the canister when it becomes magnetized, however,insufficient attractive force is exerted on the disk to draw it towardsthe canister. Thus the electromagnet device serves a "holding" functionas opposed to the "pulling" function of the conventional solenoid.

A solenoid generally has lower holding power than an electromagnet ofcomparable size and weight. Consequently, a solenoid-based system wouldbe larger and consume more raw materials and more power in operationthan an electromagnet-based system. The relatively small size of theelectromagnet-based system is also particularly advantageous in thisapplication.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially cut away perspective view of the invention inassembly with a steering column mounted shift control mechanism viewedfrom the instrument panel more-or-less toward the driver;

FIG. 2 is a sectional view of the interlock device with the shiftcontrol mechanism in PARK and the ignition switch in the Off position;

FIG. 3 is a sectional view of the interlock device with the shiftcontrol mechanism in PARK and the ignition switch in the On position;

FIG. 4 is a sectional view of the interlock device with the shiftcontrol mechanism moved out of PARK and the shift lever release membermoved away from its shift inhibit position;

FIG. 5 is a sectional view showing the gear position detents in thedetent plate; and

FIG. 6 is a schematic diagram of an electrical circuit for a brake/shiftinterlock utilizing the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a portion of an automotive vehicle steering column 10carrying a shift lever 12 for an automatic transmission, not shown. Theshift lever 12 is conventional in operation, providing a primary motionabout the axis of a pivot pin 22 parallel to the steering column 10 toshift the transmission between PARK and one of the conventional drivepositions. A PARK detent lock comprising a pawl 18 formed integrallywith the shift lever 12 and a detent plate 19 is engaged and released bya shift lever release motion about the axis of a release pin 16 held inbracket 14. The release movement, from the driver's vantage point,involves pulling the shift lever upward toward the driver to releasepawl 18 from the PARK detent in plate 19, after which the primary levermovement is enabled.

Bracket 14 and shift lever 12 are mounted on a shifter housing 17 havinga cylindrical inner bore 23 running in a direction substantiallyparallel to the longitudinal axis of steering column 10 and having anopen end adjacent shift lever 12. A shift lever release member 24 ismounted for reciprocating linear movement in bore 23. A notch 44 isformed in the member 24 between the opposite ends for purposes explainedbelow. A bias spring 26 is located at the lower end of inner bore 23 tourge release member 24 into a position in which it bears against thelower end of shift lever 12 in proximity with pawl 18. Spring 26,therefore, provides a bias force operative on the release mode of theshift lever, which bias force is easily overcome by the vehicle operatorby pulling upward on shift lever 12 to pivot it about release pin 16.Pulling upward on shift lever 12 pushes downwardly on member 24 topartially compress spring 26.

An electromagnet 28 is mounted on shifter housing 17 and is connected incircuit with the vehicle electrical system (FIG. 6) by means of anelectrical connector 32. As can best be seen in FIG. 2, electromagnet 28comprises a housing 40 for an open-ended, generally cylindrical canister36 having an axial through bore 31 which is arrayed at right angles tothe axis of motion of release member 24. Canister 36 is made of aferrous material and has an annular pocket 33 formed coaxial with bore31. A coil 30 of copper wire is wound on a spool 35 which fits insidepocket 33. An armature disk 34 made of a ferrous material is fixed to ashaft 38 which is slidably mounted in axial bore 31. A spring 42 ispositioned inside housing 40 to urge armature disk 34 and shaft 38toward release member 24. When coil 30 is energized as hereinafterdescribed, the resulting electromagnetic field magnetizes canister 36 sothat disk 34 is held firmly in contact with the open end surfaces ofcanister 36 as shown in FIG. 2 such that release member 24 is heldagainst significant movement in either direction.

When armature disk 34 is in contact with canister 36, shaft 38 extendsinto dead bolt engagement with notch 44. A chamfer 46 is preferablyformed on the left side of notch 44 and a bevel 39 is formed on shaft 38such that the two surfaces provide a cam action which forces shaft 38downward when release member 24 moves to the right (FIG. 2). Whenelectromagnet 28 is energized, however, it holds shaft 38 firmly in theextended position, so that its engagement with notch 44 effectivelylocks release member 24 in the position shown in FIG. 2. In thisposition, the shift lever 12 cannot with normal operator effort bepulled toward the driver to release pawl 18 from the PARK detent.Because the shift lever cannot with normal effort be released from thePARK detent, primary movement of the lever out of PARK is effectivelyprevented.

A key operated ignition switch 48 of the type commonly used inautomobile ignition systems is mounted on shifter housing 17 adjacentelectromagnet 28. Ignition switch 48 has an OFF position shown in FIGS.1 and 2, and an ON position shown in FIGS. 3 and 4. In the OFF position,a cam 49 pushes a bolt pin 50 against the resistance of a compressionspring 52 into housing 40 of electromagnet 28 where it prevents armaturedisk 34 from being moved away from the position shown in FIG. 2 wherethe shaft 38 extends into the notch 44 in release member 24. In the ONposition, the bolt pin 50 is retracted to permit the disk 34 and bolt 38to move downwardly as shown in FIG. 4.

Referring to FIG. 6, a circuit is shown to provide an interlock betweenthe braking system of a motor vehicle and the shifter shown in FIGS.1-5. In FIG. 6 a 12 volt automotive battery 60 is connected in serieswith electromagnet coil 30 through ignition switch 48 and a normallyclosed brake switch 64. When both switches 48 and 64 are closed, thecoil 30 is energized and the armature disk 34 is held in the positionshown in FIG. 2. Switch 64 is connected to brake pedal 62 to be openedwhen the brake pedal is depressed. Opening either of switches 48 and 64de-energizes coil 30.

OPERATION

When the vehicle operator first enters the vehicle, shift lever 12 is inthe PARK position and ignition switch 48 is in the OFF position. In thiscondition bolt pin 50 is extended to prevent movement of armature disk34 away from release member 24. Even though there is no power toenergize coil 30, shaft 38 is mechanically held in notch 44. Thisengagement holds release member 24 in the shift inhibit position inwhich it bears against the lower end of shift lever 12 to hold pawl 18in engagement with the PARK detent. This configuration prevents thevehicle operator from pivoting shift lever 12 about release pin 16 todisengage pawl 18 from the PARK detent, so the shifter is locked inPARK.

When the operator moves ignition switch 48 to the ON position, bolt pin50 moves to its retracted position in which it offers no opposition tomovement of armature disk 34 (see FIG. 3). Moving the switch 48 to ON,however, also energizes electromagnet 28 so that armature disk 34 ismagnetically held against the face of canister 34 and shaft 38 is firmlymaintained in the extended position. The release movement of the gearshifter continues to be inhibited. Because of the chamfered face ofnotch 44, the interlock can be overcome by the application of greaterthan normal force to the shift lever 12.

When the operator depresses the vehicle brake pedal 62, switch 64 opensand coil 30 is de-energized, thus removing the electromagnetic forcethat holds shaft 38 in its extended position. When the operator pivotsshift lever 12 about release pin 16, release member 24 is relativelyeasily pushed toward the position shown in FIG. 4 and the interactionbetween bevel 39 and chamfer 46 forces shaft 38 to its retractedposition. The operator is now able to move shift lever 12 about pivotpin 22 and thereby shift the transmission out of PARK.

In the preferred embodiment of the invention, bevel 39 and chamfer 46are shaped so that if the vehicle operator is pulling on shift lever 12at the time coil 30 is de-energized, the force being applied to releasemember 24 will not result in binding between notch 44 and shaft 38 thatmight prevent movement of shaft 38 to its retracted position. Thispreload release geometry is described in detail in U.S. Pat No.5,176,231, issued Jan. 5, 1993 and assigned to Pontiac Coil, Inc. ofWaterford, Mich., the disclosure of said patent being incorporatedherein by reference.

The mechanism as described provides another vehicle safety feature inthat ignition switch 48 can only be returned to its OFF position ifshift lever 12 is first placed in PARK. This prevents the ignition keyfrom being removed from ignition switch 48 until the vehicle is stoppedand the transmission is in PARK.

An advantage of the mechanism described is that no sound audible to thevehicle operator will be produced when the brake interlock isdeactivated by application of the vehicle brakes.

As is apparent from the above description and accompanying drawings, thepresent shift interlock mechanism provides a simple, compact, andreliable means by which to prevent a vehicle transmission shift leverform being moved out of PARK and into a driving gear range until theignition switch 48 has been placed to the ON position and the brakepedal 62 has been depressed. The interlock mechanism adds a minimum ofmoving parts to the shifter, and the integration of the ignition switchand brake interlocks is executed so that the mechanism will easily fitinside of a steering column.

It will be appreciated that the drawings and description containedherein are merely meant to illustrate a particular embodiment of thepresent invention and are not meant to be limitations upon the practicethereof as numerous variations will occur to skilled persons. Forexample, the interlock mechanism may be moved to the console in whole orin part. Although the elimination of cables is advantageous, ignitionlock 48 may be connected to bolt pin 50 with a cable if a remotelocation is desired. The coil 30 may be interlocked not only with abrake switch, but any switch operable within the vehicle's electricalsystem.

I claim:
 1. A shifter interlock for an automotive vehicle comprising:ashifter of the type in which a release movement of a shift lever removesthe shifter from a shift lock position and thereby permits a primarymovement of the shift lever into and out of a PARK position; a releasemember linearly movable between a first position in which it inhibitsshift lever release movement and a second position in which it enablesshift lever release movement; a locking device comprising anelectromagnet having a canister and an armature, a non-ferrous shaftattached to the armature, and a spring, energization of theelectromagnet holding the armature against the canister such that theshaft is in a direct interfering relationship with the release member tooppose movement of the release member away from its first position, andthe spring urging the armature and the shaft toward the interferingrelationship; and an electrical power circuit connecting theelectromagnet with a vehicle power supply and including at least oneswitch for selectively energizing and de-energizing the electromagnet.2. The mechanism of claim 1 in which the release member and the shaftare operatively associated such that when the electromagnet isde-energized, movement of the release member away from its firstposition causes the shaft to move out of the interfering relationship.